It turned out to be quite simple to build one, note that mine is about half the size of a usual one so it probably will need to be pumped faster than the usual box bellows. The valves are just pieces of wood with yarn threaded through them and two holes above the valves. As it is I need to seal the top, grind down the piston a bit and add padding around it and make the side housing to join both output valves. All in all it should take some one a day to build using a drill and a jigsaw, but I'm slower than most.
Note: I'm not going to attach the bottom panel, once this thing is set into the ground, there really is no reason to attach it and it will make maintenance much easier. Will also making getting rid of animals easier should they decide to make a nest out of it.
Edited by nabiul, 12 January 2008 - 08:03 PM.